消息发送

在 Smalltalk 中，你所做的几乎所有操作都是向对象发送消息 （在其他语言中称为调用方法）。有三种类型的消息：

一元信息：

#(1 2 3) size
"This sends the #size message to the #(1 2 3) array.
 #size is a unary message, because it takes no arguments."

二进制消息：

1 + 2
"This sends the #+ message and 2 as an argument to the object 1.
 #+ is a binary message because it takes one argument (2)
 and it's composed of one or two symbol characters"

关键字消息：

'Smalltalk’ allButFirst: 5.
"This sends #allButFirst: with argument 5 to the string 'Smalltalk',
 resulting in the new string 'talk'"

3 to: 10 by: 2.
"This one sends the single message #to:by:, which takes two parameters (10 and 2)
 to the number 3.
 The result is a collection with 3, 5, 7, and 9."

语句中的多个消息按优先顺序进行评估

unary > binary > keyword

从左到右

1 + 2 * 3 " equals 9, because it evaluates left to right"
1 + (2 * 3) " but you can use parenthesis"

1 to:   #(a b c d) size   by:   5 - 4
 "is the same as:"
1 to: ( #(a b c d) size ) by: ( 5 - 4 )

如果要向同一对象发送许多消息，可以使用级联运算符 ;（分号）：

OrderedCollection new
  add: #abc;
  add: #def;
  add: #ghi;
  yourself.

“这首先将消息#new 发送到 OrderedCollection 类（#new 只是一个消息，而不是运算符）。它会产生一个新的 OrderedCollection。然后它将新的集合发送三次消息#add（带有不同的参数），和你自己的信息。“